There are a number of applications for dimly lit lamps and small but identifiable lights in which power drain must be very small. The floating disc toy, sometimes called a "sport disc," is one example. Shaped like an inverted shallow bowl, the floating disc is held at one edge, open side down, and is thrown or "sailed" with a side arm motion. It spins as it moves, and it quickly slows in its movement away from the thrower to a near standstill. Near the end of its travel it seems to float or hover and is readily caught by a second player.
The floating disc is inexpensive, permits play with two players, or any number more than two players. It is easily carried, can be played with in any reasonably open space, and disparity of age of players is not a limiting factor in play. For these reasons, and others, play with floating discs is popular at picnics and other outings, and is popular for street play. However, as with many games, play must end if the disc cannot be seen or its position identified.
Fortunately, the floating disc moves slowly toward the end of its travel, and its orientation (open side down) remains nearly the same. It can be readily seen, and play can continue after dark if the disc carries lights. The lights need not be so bright as to furnish illumination beyond the disc. It is enough if the lights glow only brightly enough to be seen at a distance of fifty to one hundred feet. However, effective play is possible only if the catcher can "see" the rim of the disc.
Persistence in the catcher's optical system helps greatly. Since the disc is spinning, lighting a lamp at its edge will create the illusion of a circle of light. However, a lamp placed so that it is visible through a complete or nearly complete turn of the disc would necessarily protrude or project from the disc and be subject to damage when the disc was not caught. Even worse, it might injure the catcher if caught.
Such considerations in the case of floating discs and other practical problems in the case of other applications, particularly in toys, often lead to a requirement for greater amounts of energy. When energy is to be supplied by an electrical battery, the requirement for more energy translates into increased cost and increased size and weight. Increases in those elements of a design usually can have a profound effect on the toy or other apparatus for which lights are but an accessory. In the case of the floating or sport disc, the problem has been to find a lighting system which will provide enough light for nighttime play which will provide an acceptable compromise between battery weight and "floating" characteristics of the floating disc, and which can be provided at a price that users can be expected to be willing to pay. That problem has gone unsolved until the making of this invention.